The present invention relates to an automatic travelling apparatus capable of identifying a permissible travel path for the purpose of permitting a vehicle to automatically run along a road.
Recently, there has been developed an automatic travelling apparatus which is capable of identifying a permissible travel path, setting a target course thereon, and steering a vehicle to follow the target course.
The automatic travelling apparatus disclosed in Japanese laid open patent publication No. 199610-88 generates an image of an area ahead of a vehicle in its running direction using an image pick-up device which is fixed to the vehicle. The apparatus determines, by processing the generated image, a permissible travel path in an X-Y coordinate system wherein the Y-axis corresponds to the axis of the vehicle's running direction. The apparatus sets a target course in the determined permissible travel path, and estimates an amount of steering necessary to permit the vehicle to run along the target course based on a currently detected running condition of the vehicle.
While negotiating a curve, the vehicle whereon the above-mentioned apparatus is mounted may encounter slippage depending on its running speed. Thus, the monitoring direction of the image pick-up device may deviate from the actual running direction of the vehicle. The difference between the monitoring direction of the image pick-up device and the actual running direction of the vehicle is referred to as the side-slip angle.
Accordingly, while the vehicle runs with a side-slip angle, the image pick-up device can not monitor the actual course of the vehicle, that is, the Y-axis of the X-Y coordinates does not stand for the actual running direction. If in such a situation a steering correction is estimated with respect to a target course set in a permissible travel path, the steering correction may contain an error corresponding to the side-slip angle of the vehicle, thereby inhibiting the ability of the vehicle to follow the target course.